Conventionally, in a master/slave type POS (point-of-sale) system, the master unit sequentially designates the respective slave units (e.g. electric cash registers (ECRs) as POS terminals) according to a polling system to enable the collection or consolidation of sales data or the transferring of set data, or an inquiry with respect to inventory. That is, the master unit designates, one by one, the associated ECRs in a predetermined sequence to perform processing such as the collection, consolidation, etc., of data.
In this way, the master unit manages all the slave units and effects operations such as the collection and consolidation of data, thus placing a burden on the master unit. Where the master unit, in particular, serves as an ECR, there is the problem that the master unit per se cannot perform a registration of sales data until it has finished effecting processing on the last slave unit.